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f4b01a9edf
k_tanf.c but with different details. The polynomial is odd with degree 13 for tanf() and odd with degree 9 for sinf(), so the details are not very different for sinf() -- the term with the x**11 and x**13 coefficients goes awaym and (mysteriously) it helps to do the evaluation of w = z*z early although moving it later was a key optimization for tanf(). The details are different but simpler for cosf() because the polynomial is even and of lower degree. On Athlons, for uniformly distributed args in [-2pi, 2pi], this gives an optimization of about 4 cycles (10%) in most cases (13% for sinf() on AXP, but 0% for cosf() with gcc-3.3 -O1 on AXP). The best case (sinf() with gcc-3.4 -O1 -fcaller-saves on A64) now takes 33-39 cycles (was 37-45 cycles). Hardware sinf takes 74-129 cycles. Despite being fine tuned for Athlons, the optimization is even larger on some other arches (about 15% on ia64 (pluto2) and 20% on alpha (beast) with gcc -O2 -fomit-frame-pointer). |
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